Problem: Simplify the following expression: $n = \dfrac{1}{8a} - \dfrac{10}{3a}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8a$ and $3a$ $\lcm(8a, 3a) = 24a$ $ n = \dfrac{3}{3} \cdot \dfrac{1}{8a} - \dfrac{8}{8} \cdot \dfrac{10}{3a} $ $n = \dfrac{3}{24a} - \dfrac{80}{24a}$ $n = \dfrac{3 -80}{24a}$ $n = \dfrac{-77}{24a}$